In any mobile communication system, channel capacity and communication resource availability are a concern for both the system operator and mobile users. Mobile users desire to have readily available access to communication resources, and system operators want to maintain a level of quality in the communication resources it offers so that, even when a particular cell or serving area is operating at capacity, other users in the serving area who desire access to communication resources do not interfere with users presently using communication resources.
Access noise is the noise generated by users seeking access to communication resources in spread spectrum communication systems. The noise comes from the imperfect orthogonality of the spreading codes used in these systems and, in particular, at two times namely, when mobile stations request access to communication resources and when mobile stations negotiate for particular communication resources. A mobile station may request access and, upon negotiation for a particular quality of service, find the desired resource is not available. The process of negotiating and ultimately failing to obtain the desired communication resource adds noise to the other channels.
In general the noise effect of imperfect orthoganality has been addressed in the past by techniques such as discontinuous receive and transmit. In each of these techniques, when a transmitter has no information to transmit, such as when a user of the communication transceiver is not presently speaking, the transceiver doesn't transmit anything. On average these techniques reduce the noise each channel experiences. However, conventional spread spectrum communication systems all require mobile stations to request and negotiate service, whether such service is available or not, and this access noise is not addressed by discontinuous transmit techniques. Therefore there is a need for a way by which access noise can be reduced.